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DROP TABLE IF EXISTS t_test;

CREATE TABLE t_test (

bs bigint(20) NOT NULL auto_increment,

username varchar(20) NOT NULL,

password varchar(20) default NULL,

remark varchar(200) default NULL,

PRIMARY KEY (bs)

) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=gbk;

INSERT INTO t_test VALUES (1,'lavasoft','123456',NULL);

INSERT INTO t_test VALUES (2,'hello',NULL,NULL);

INSERT INTO t_test VALUES (3,'haha',zz,tt);

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update t_test t

set t.password = '***'

where t.bs = 2;

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update t_test t

set t.password = '*', t.remark = '*'

where t.bs = 1;

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update t_test t

set t.password = null, t.remark = null

where t.bs = 3;